The value of spectroscopy as an analytical tool is limited by its accuracy and reliability. Although spectroscopy can be used to identify and quantify substances in many environments and applications, different types of interferences can detrimentally influence the extraction of useful information from a spectrum. One type of interference, characterized as etalon noise, behaves chaotically and can disguise or distort accurate data. Etalons are patterns of light caused by reflections in the optical path of the source used in the spectroscopic technique. The etalons can cause constructive and destructive interference with the signal at certain wavelengths of light.
Traditionally, efforts to reduce etalon noise have focused either on the physical design of the spectroscopic device or on mathematical modeling. Both areas have seen repeated failures. Etalons could, theoretically, be minimized by creating the optimal instrument design, but progress in this area has stalled for a number of years. In addition, attempts have been made to derive a mathematical formula describing the behavior of the etalons. Unfortunately, the etalons can instantaneously change configurations to give multiple allowable solutions to a formula.
Regardless of which traditional approach is used to characterize etalon noise, they are inaccurate and slow. In a specific application, such as oil drilling, spectroscopy is used to detect subterranean gases in real-time. The previous methods do not allow for computation at speeds needed for real time measurements. Calibration of the instrument takes too long and as the instrument may be located hundreds of feet below the surface of the earth in a hole, it would be inaccessible for calibration and adjustment. A solution is needed that reduces the etalon noise in a spectrum in a quick, reliable way.